As a light-emitting element, there has been widely known an element that includes, on a monocrystalline substrate such as a sapphire substrate, a layer having a function as a light-emitting element in which one or more semiconductor layers and the like have been laminated (light-emitting element layer). In the light-emitting element having such layer construction, a pair of electrodes is formed by providing in order of: a first electrode; a light-emitting element layer; an insulating monocrystalline substrate; and a second electrode in the thickness direction of the element.
Available as a method of manufacturing a light emitting diode (LED), which being one kind of light-emitting element, is a laser lift-off technology involving: forming the LED as a light-emitting element layer on a sapphire substrate; and then peeling the sapphire substrate with a laser. The employment of the laser lift-off technology enables the formation of a vertical LED that allows a large current to flow. However, the technology has been poor in yield because the sapphire substrate is hard to be completely peeled with the laser, and damage to the LED may also be caused by the laser.
In view of the foregoing, for electrically connecting the light-emitting element layer and the second electrode, there has been disclosed a manufacturing method involving: forming a vertical hole across the monocrystalline substrate so as to penetrate the monocrystalline substrate in its thickness direction, and filling a conductive material into the vertical hole; or forming the material into a layer shape in the hole, to thereby secure conduction between the light-emitting element layer and the second electrode (see Patent Literatures 1 to 4). In addition, when a buffer layer is further formed between the light-emitting element layer and the monocrystalline substrate, a vertical hole that penetrates the thickness directions of the monocrystalline substrate and the buffer layer is formed, and then the conductive material is filled into the vertical hole (see Patent Literatures 1, 3, and 4). The employment of such manufacturing method leads to an improvement in yield because the method eliminates the need for completely peeling the monocrystalline substrate from the light-emitting element layer.
In each of the technologies described in Patent Literatures 1 to 4, the vertical hole is formed by utilizing any one of various etching methods such as dry etching and laser ablation after forming at least part of the respective layers forming the buffer layer and light-emitting element layer to be formed on the monocrystalline substrate.